There is known an apparatus for drifting openings in hard rock referred to as heading combine (cf. French Pat. No. 2,193,138) incorporating a baseplate, a first carriage mounted on said baseplate, a trough-shaped carrier attached to the first carriage so as to be capable of rotating about the vertical axis, a boom extending parallel to the longitudinal axis of the baseplate and fitted with due regard for rotation on the trough-shaped carrier about the horizontal axis as well as with due regard for rotation about its own longitudinal axis, a turntable fitted to the frame with provision for rotation about the horizontal axis and located at--or contiguous with--the outside end of the boom, a second carriage serving to provide support for an operating mechanism and fitted with provision of sliding relative to the turntable.
Apart from that, the combine is provided with means of mucking comprising a winch and a scraper bucket, the winch being arranged in the wake of the machine--preferrably on the baseplate or linked up with same by means of a rope and sheave--and the scraper bucket working ahead of the combine and being linked up with said winch.
The first carriage is capable of travelling along the baseplate with the aid of double-acting hydraulic jacks.
The trough-shaped carrier is capable of turning on the first carrier to which it is fitted and about the vertical axis through an angle of 45.degree. either side from the longitudinal axis of the machine also with the aid of double-acting hydraulic jacks.
The boom located on the trough-shaped carrier can be turned by a pair of double-acting jacks either through 35.degree. upwards or 10.degree. downwards from the horizontal axis. In addition, the boom can be rotated through 360.degree. about its own longitudinal axis by a mechanism incorporating two hydraulic jacks and a rack and pinion, the pinion being attached to the boom.
The turntable fitted to the front end of the boom is capable of turning with respect to said boom starting from a position parallel to the longitudinal axis thereof and ending in a position at right angles to the same longitudinal axis of the boom, being acted upon by respective double-acting jacks.
The second carriage which is fitted to said turntable and serves to hold fast a means of breaking can be displaced along the longitudinal axis of the turntable by a double-acting hydraulic jack.
All the jacks operate from a hydraulic system incorporating an oil tank, a pump with a motor, piping, and various control and safety valves. The hydraulic system is manually controlled from an operator's seat available on the trough-shaped carrier.
In operation, the means of breaking is fed and its tool is pressed to the rock at the point where this should be broken by the above components of the machine. After that a ram of the means of breaking strikes against the tool transmits the energy of the impact to the rock which is consequently disintegrated. On breaking off a lump of rock, the means of breaking is reset into the working position and the next stroke is applied. The broken rock is removed with the aid of the scraper bucket and winch.
The apparatus for drifting openings in hard rock described above is of a rather complicated construction, featuring numerous hydraulic jacks and pivoted members. The percussive means of breaking used in this apparatus requires careful setting so that its longitudinal axis and the coinciding axis of the tool are essentially at right angles to the solid rock at the point of striking. When a lump of rock falls down after the stroke the tip of the tool interacting with the rock is likely to slip along the surface thereof at an angle with the axis of the means of breaking which is far from being a right one. Said slippage may impose dynamic loads of considerable magnitude on all elements of the apparatus, and--since these loads are limited only by the amount of yielding said elements are capable of--there is the danger of a breakdown.
Obviously, constructional intricacy and the phenomenon of slippage of the breaking tool described above impair the operational dependability of the known apparatus to a considerable extent.
The necessity of setting the means of breaking at right angles to the solid rock each time preparatory to the stroke entails considerable losses of operating time and, consequently, reduces the efficiency of breaking.
Also known is another apparatus for drifting openings in hard rock referred to as hard-rock mining machine (cf. U.S. Pat. No. 3,863,989). It has a manipulator frame extendable in height so as to thrust against the roof and floor of the opening through the intermediary of an upper and a lower means of support, respectively. The manipulator frame carries a percussive means of breaking with a reciprocating rock-crushing tool, said means being fitted to the frame so as to be capable of turning in the horizontal and vertical planes for working on the face systematically over its entire breast.
Linked up with the means of support of the manipulator frame is a means of thrust serving as a carrier with respect to which said frame is capable of moving along the opening integrally with the percussive means of breaking. Said means of thrust is provided with a headpiece and skids extending next to and along the side walls of the opening, said headpiece of the means of thrust and the upper means of support. of the manipulator frame forming a canopy which provides support for the roof.
The manipulator frame, in its turn, incorporates a base plate with vertically-fitted thrust cylinders and a transverse girder with uprights which pass through guide sleeves and rest on the movable parts of the thrust cylinders, including the pistons and piston rods. The guide sleeves are attached to two sidepieces fitted to said base plate.
The percussive means of breaking is fitted to a horizontal shaft supported by bearings in two said sidepieces and capable of rotating in the vertical plane by virtue of a hydraulic cylinder. A spherical joggle provided in the middle of the transverse girder of said manipulator frame engages a spherical recess in the upper means of support so that a pivot joint is formed which links up the manipulator frame with said upper means of support. A drum situated at the bottom of the manipulator frame below the base plate is girdled by a chain the ends of which are connected to a hydraulic cylinder installed on the lower means of support. Said drum, in conjunction with the rest of above mentioned components interacting therewith, serves the purpose of turning the manipulator frame integrally with the percussive means of breaking in the horizontal plane.
Available in the lower end face of the drum is a spherical recess which is engaged by a spherical joggle secured to the lower means of support so that a pivot joint is provided between the base plate of the manipulator frame and the lower means of support.
Said means of thrust is provided with two hydraulic cylinders fitted to the skids so that the movable components of said cylinders provide support for the uprights passing through the guide sleeves which are attached to struts rigidly linked up with the skids. Resting on the spherical heads of said uprights is the headpiece of the means of thrust. The skids are interlinked with each other by a stack of laminate plate springs capable of an elastic deformation thanks to which the skids readily negotiate surface irregularities of the floor when the machine is on the move.
The skids are linked up with the lower means of support of the manipulator frame through the intermediary of two hydraulic cylinders, and another pair of hydraulic cylinders interlinks the upper means of support of the manipulator frame with the headpiece of the means of thrust.
The rock-breaking procedure is as follows. The rock-crushing tool is set to reciprocate, striking at the same point on the face until the rock breaks off within the depth of the layer excavated. After that the means of breaking is turned in either the vertical or horizontal plane so as to be aimed at an adjacent point and the breaking goes on in said sequence of events over the entire face breast. The muck is removed from the working zone by any known means of loading and hauling.
When rock is being broken by the percussive means of breaking, the manipulator frame is held fast due to its means of support which are thrust by the relevent hydraulic cylinders against the roof and floor of the opening. To advance the machine, the means of thrust takes over, its hydraulic cylinders exerting a thrusting action against the roof and floor, while the manipulator frame is relieved of the thrust applied thereto. Next the manipulator frame is advanced with the aid of the hydraulic cylinders interlinking the frame with the means of thrust. Once in a new position, the manipulator frame is again held fast by its thrustable means of support whereas the means of thrust is set free and is dragged into a new position in the wake of the manipulator frame by said hydraulic cylinders interlinking said frame with said means of thrust. Thus, the machine is advanced over the working in accordance with the known principle of walking.
In the described apparatus for drifting openings in hard rock, the operation of the percussive means of breaking sets up high dynamic loads on its components, said loads occurring mainly either after oblique strokes, i.e., those when the percussion tool travels before the stroke over a path deviating from the normal to the surface of rock at the point of impact, or after idle strokes when the tool fails to meet the rock at the end of its travel towards the face. This latter phenomenon is a quite frequent occurence partly observed every third to fifth stroke depending on the conditions, for the rock breaks off in a manner which is a rather irregular one.
In addition to impairing the dependability of the apparatus to a considerable extent, said loads have also an adverse effect on the hydraulic cylinders serving to turn the means of breaking in the course of manipulation in that they trigger safety valves, bring about leaks of fluid from said cylinders and, as a result, cause the means of breaking to miss the point it is necessary to strike at. Said deviations of the means of breaking call for additional manipulation so as to aim at the point and this, in its turn, reduces the efficiency of breaking.